CN102622357A

CN102622357A - Method for single write-in on basis of fat32 file system format

Info

Publication number: CN102622357A
Application number: CN2011100296952A
Authority: CN
Inventors: 邹芬
Original assignee: SAIKUTE (BEIJING) INFORMATION TECHNOLOGY Co Ltd
Current assignee: SAIKUTE (BEIJING) INFORMATION TECHNOLOGY Co Ltd
Priority date: 2011-01-27
Filing date: 2011-01-27
Publication date: 2012-08-01

Abstract

The invention provides a method for single write-in on basis of a fat32 file system format and belongs to the technical field of information safety. The method solves the problems of unsafe factors that in the prior art, important information is modified after stored and is deleted mistakenly and the like. The method comprises dividing a storage space for plane addressing according to the fat32 format on the basis of the fat32 file format, judging instructions of storage, modification, deletion and the like according to a zone bit in a fat32 file system on the basis of a framework of the file system, and accordingly controlling the instructions of storage, modification, deletion and the like of the information. The method improves safety of the important information.

Description

A kind of method that writes based on single under the fat32 file system format

Technical field

The present invention relates to a kind of method that writes based on single under the fat32 file system format, a kind of method that writes based on single under the fat32 file system format belongs to field of information security technology.

Background technology

At present, Information technology flourishing day by day today, electronic storage device has obtained using widely, and common memory device has hard disk, and USB flash disk etc. are based on the memory device under the fat32 file system.Fat32 is a kind of of system memory devices zoned format.This form adopts 32 file allocation table, its managerial ability to memory device is strengthened greatly, has broken through fat16 has only 2GB to the capacity of each subregion restriction.Because present memory device production cost descends, its capacity is increasing, and behind the zoned format of utilization fat32, we can be defined as a memory device subregion and needn't be divided into several subregions uses, greatly facilitate the management to memory device.Generic storage equipment can be carried out reading writing working on computers through the equipment of USB interface.This series products has brought very convenient service to the user.But the specific demand that is based in the application can't realize, writes indegree like restriction. as if the storage means that this single that the present invention mentions writes can not delete after the storage for general user's quite inconvenience after all, and single has just cancelled after finishing using.But still there is the user of specific area that demand is in this respect arranged; Data storage during for example the public security system evidence is gathered; In being used in the purposes of searching warrant, write down important penal roll in a large number; Can not only avoid intentionally that the personage attempts to alter data, can also guarantee that data in the memory device can permanent storage wherein and not lose or damage.At traffic system and aircraft black box thereof, also there is the wide space that utilizes in instrument data record field in addition.Therefore prior art need be improved and improve.The invention provides a kind of method that writes based on single under the fat32 file system format, the blank of art technology is provided.

Summary of the invention

For solving the problems of the prior art, the present invention provides a kind of method that writes based on single under the fat32 file system format.Said method comprises based under the fat32 file layout; Divide the storage space of flat addressing according to the fat32 form; On the framework of file system, screen instructions such as memory modify deletion, control thereby information stores revised instruction such as deletion according to the zone bit in the fat32 file system.Thereby improved the security of important information.Protection to file is more reliable.

For the better protection file is not illegally modified, a kind of method that writes based on single under the fat32 file system format.Said technical scheme is following:

A kind of method that writes based on single under the fat32 file system format: said method comprises:

Step 1, initialization fat32 file system.The fat32 file system structure is analyzed, calculated reference position, the sector-size of fat table, the reference position of root directory, and be recorded in the hardware device.

Step 2, receive the read write command of external system through the usb communication module.

Step 3, the outside write order operation requests of analysis.

Affiliated step 3 also comprises:

The sectors of data of write order is read out and the comparing of write data, and read.

If revising first byte of the directory entry of root directory is 0xE5, show that then this communication wants the file of delete file system, then forbid this communication.

Judge location revision, the value of revising the FAT list item is 0x00000000, shows that then this communication wants the file of delete file system, then forbids this communication.

Judge location revision,, and indicate that the byte of the sector in the ban of sector is 0x02, show that then this communication is to remodify file, forbids this communication if modification is the data field.If the byte of the sector in the ban of sign sector is 0x00, then allow this communication.

Description of drawings

Fig. 1 is the information protection process flow diagram in the embodiment of the invention.

Embodiment

For making the object of the invention, the more clear accompanying drawing that below will combine of technical scheme and advantage is described further embodiment of the present invention.

Technical scheme of the present invention will solve unsafe factors such as being modified and missing deletion action in the prior art after the important information storage.On the framework of file system, differentiate storage and revise instructions such as deletion, thereby instructions such as information stores modification deletion are controlled according to the zone bit in the fat32 file system.

Embodiment

The invention provides a kind of method that writes based on single under the fat32 file system format

Step 1: initialization FAT32 file system.The FAT32 file system structure is analyzed; Read first sector of file system; If first byte of first sector is 0xEB; Show that first sector is the DBR sector, indicated the file system relevant information in the DBR sector, write down sector-size, each bunch and had the number of several sectors, file system FAT table, FAT table size, first root directory bunch number, the number of reserve sector, calculate the reference position of FAT table.Thereby draw the start sector number of FAT table, first catalogue bunch place sector number, and be recorded in the hardware device.

Step 2: the read write command that receives external system through the usb communication module.Through the order of the outside Usb Mass Storage agreement of usb communication module reception, from order, extract the start address and the sector number of read write command, read-write sector.

Step 3: analyze outside write order operation requests.

The sectors of data of write command is read out and the comparing of write data, and read.If operational order extracts the sevtor address of writing the sector for writing sector data from order,, confirm to write sector number and belong to which scope according to FAT table and the root directory sector number that step 1 draws.Belong to FAT table scope if write sector number; Show that this time operation will be revised the data under the FAT sector, then read all data under the current sector number earlier and will write sector data and do comparison; If the value of a certain FAT item is non-vanishing and the value of the data buffer corresponding FAT item down that will revise is zero; Show that it is zero that operation this time will be revised the value of FAT item, belongs to file or data under the deletion FAT32 file system, so undo.Belong to the root directory scope if write sector number; Show that this time operation will be revised the data under the directory sector; Then read all data under the current sector number earlier; With to write sector data and do comparison, if first byte of the document directory structure under the current sector is not 0xE5 for 0xE5 and first byte that will revise the corresponding document bibliographic structure body the data buffer under, show that the purpose of this time operating is that first byte of revised file bibliographic structure is 0xE5; Belong to deletion FAT32 file system bibliographic structure, so undo.Belong to the data sector scope if write sector number, show and to revise the data content that has had file when this time operating or add file content for the first time.Read the byte under the current sector number under the sign sector earlier,, show that this data sector was not write, then allow this time to operate correct execution, and this byte content is rewritten as 0x01 if this byte content is zero.If this byte content is non-vanishing, show that this data sector is modified, then do not allow to revise undo once more.

Claims

1. method that writes based on single under the fat32 file system format, its technical characterictic is, comprises the steps:

A initialization fat32 file system is analyzed the fat32 file system structure, calculates reference position, the sector-size of fat table, the reference position of root directory, and is recorded in the hardware device;

B receives the read write command of external system through the usb communication module;

C analyzes outside write order operation requests, and judges;

D writes data and authorizes according to judging the exterior read-write order.

2. a kind of method that writes based on single under the fat32 file system format according to claim 1 is characterized in that said steps A also comprises:

The FAT32 file system structure is analyzed, read first sector of file system, and be recorded in the hardware device.

3. a kind of method that writes based on single under the fat32 file system format according to claim 1 is characterized in that said step also comprises:

Analyzing outside write order operation requests, do comparison with the target sector data, is zero if this operation will be revised the value of FAT item, belongs to file or data under the deletion FAT32 file system, undo.

4. a kind of method that writes based on single under the fat32 file system format according to claim 1 is characterized in that said step also comprises:

When writing sector number in the root directory scope; First byte of judging the document directory structure under the current sector is not that 0xE5 and first byte that will revise the corresponding document bibliographic structure body under the data buffer are 0xE5; Belong to deletion FAT32 file system bibliographic structure, undo.